A descriptive study of the equine proximal interphalangeal joint using magnetic resonance imaging, contrast arthrography, and arthroscopy.
Authors: Kamm J Lacy, Goodrich Laurie R, Werpy Natasha M, McIlwraith C Wayne
Journal: Veterinary surgery : VS
Summary
# Editorial Summary This cadaveric study mapped the anatomical landscape of the equine proximal interphalangeal joint to establish safe and effective arthroscopic access routes, addressing a critical gap in surgical technique standardisation. Using multimodal imaging (MRI, computed tomography with contrast arthrography) and direct arthroscopic visualisation of 36 limbs from 15 horses, the researchers identified which joint regions could be safely accessed and, equally important, which vital structures demanded avoidance during portal placement. Arthroscopy via dorsal and palmar/plantar approaches provided visibility of approximately 62% of the joint perimeter with comparable views regardless of whether the arthroscope was inserted proximal or distal to the PIP joint itself, though proximal placement 1.5 cm above the joint line offered superior instrument manipulation. The abaxial (lateral and medial) articular surfaces remained consistently difficult to visualise due to joint pouch narrowing, whilst palmar/plantar portals required careful positioning dorsal to the neurovascular structures and proximal to the middle phalanx epicondyle to avoid iatrogenic tendon and ligament damage. For practitioners performing PIP joint arthroscopy, these findings provide evidence-based portal placement guidelines that optimise visualisation whilst minimising soft tissue trauma—particularly valuable information given the PIP joint's role in lameness and its challenging anatomy.
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Practical Takeaways
- •Use the 1.5 cm proximal approach to the dorsal PIP joint pouch for optimal arthroscope manipulation and visualization during diagnostic or therapeutic procedures
- •Position palmar/plantar portals dorsal to the neurovascular bundle and proximal to the epicondyle to avoid iatrogenic soft tissue damage
- •Recognize that abaxial articular surfaces of the PIP joint have limited arthroscopic visibility and may require alternative imaging or approaches for complete assessment
Key Findings
- •62.4% of the PIP joint perimeter is arthroscopically observable from dorsal and palmar/plantar pouches with no significant difference between proximal (1.5 cm) and distal approaches (P=0.59)
- •Dorsal and palmar/plantar joint pouches provide adequate visualization of axial articular surfaces of proximal and middle phalanx
- •Abaxial articular surface portions are difficult to visualize due to joint pouch narrowing
- •Palmar/plantar portals positioned dorsal to neurovascular bundle and proximal to middle phalanx epicondyle minimize risk of tendon and ligament injury